The "swing state" argument is simply a lie. Obama can make states like Virginia and North Carolina into swing states, without losing states like Ohio as possible "blue" states at the same time. Why? Because even though Barack lost to Hillary in Ohio, he's going to be going head-to-head against a rabid "free trader" in the general election. They may have doubts about Obama's commitment to changing NAFTA - thanks to well planned and timed dirty tricks - but they should have no doubt that McCain won't even consider making any changes to it.
The simple fact is that Barack is emmanantly more electable than Hillary is. He brings an energized group of supporters with him that have historically not been involved much, and he doesn't generate sheer hatred from the right. Both of those things change when Hillary is the nominee (the notion that "the conservatives don't hate her" that one or two of her supporters keep pushing is laughable to anybody that paid attention during the Clinton presidency). She simply can't win, and I've been saying that for as long as her candidacy has been talked about (and well before I ever stated that she wouldn't get my vote).
One of the things that tipped me to Obama's side is what you just said. He is simply more electable and has the appeal of purple states, especially VA. I see so many Obama bumper stickers and signs up here in Northern VA. And Foster's win last night shows the strength of an Obama ticket.